Brake



Dec. 21, 1937. E. G. CARROLL J 2,102,834

BRAKE Original Filed Nov. 11, 1930 2 Sheets-Sheet 2 F1543 www Jaw/CM llllllllllm 5 xxx x x 1 mil/#1113155!!! INVENTOR. EUGENE G. CHREOLL ATTORNEY.

-45 the pressure liquidto Patented Dec. 21, 1937 BRAKE Eugene G. Carroll, Los Angeles, Calm, assignor to UNITED STATES PATENT OFFlC Bendix corporation of Illino Original application November 11,

Brake (lom lisany, South Bend, Ind., a

1930, Serial No. 494,993. Patent No. 2,018,912, 'dated October 29, 1935. Divided and this application Janu'ary 14, 1935, Serial No. 1,617

1 Claims. (01. era-54.8 i

This application is a division of my copending application Serial No. 494,993, filed Nov. 11, 1930 and issued as Patent No. 2,018,912, Oct. 29," 1935.

The invention relates to hydraulic brake appab ratus. The braking power of trucks is generally found inadequate to stop a truckwithin a suinciently short distance to preventlaccidents, particularly where the trucks are heavy and carrying a heavy load. In trucks of 6-wheel type, if hy- 10 draulic brakes are installed on all the wheels, the

actuation of the usual brake pedal .does not readunder pressure, for example, in 6-wheel brake installations, though it is to be understood that Q 25 my invention is also applicable to brake installahaving less or more than.

tions on automobiles six wheels.

The invention may be applied in a new installation of hydraulic brakes, but one of my objects 39 is to provide a construction which may be applied as an attachment to hydraulic brake apparatus already installed in a car to enable thehydraulic pressure to be readily increased as may be desired, for example, with my improvement the hydraulic '35 pressure in applying the brakes can be raisedfrom 250 or 300 pounds. per square inch to approximately 500 or 600 pounds per square-inch.

One of the difllculties in developing a high pressure in the present systems is that the brake is usually applied by a foot lever giving a stroke of about an inch and a quarter to the piston that develops the pressure. According to my invention' I provide additional means operated by a hand lever for displacing an increased volume of boost the pressure already developed.

A further object of the invention is to provide means for insuring the proper operation of the apparatus b'y insuring the operation of the two 50 controlling levers,

hand-lever, in the proper order.

A further object of the invention is to provide a master cylinder for hydraulic brakes of this type with a booster chamber to insure a full com- 55 pression chamber when the compressing plunger number of brake cyl-- inders to be served effectively with the liquid,

the invention, it should that is, the foot lever and the moves forward and to provide means for relieving the pressure in advance of the booster head after the boosting effect has been attained, thereby enabling the entire force to be exerted in raising the pressure in the compression chamber.

Further objects of the invention will appear hereinafter. v

The invention consists inthe novel parts and combination of parts to be described hereinafter, all of which contribute to produce an efllcient 'hydraulic .brake apparatus forheavy vehicles.

A preferred embodiment of the invention is described in the following specification, while the broad scope of the invention is pointed out in the appended claims. In the drawings:

Figure 1 is a diagrammatic plan illustrating the apparatus as applied to a four-wheel brake installation.

Figure 2'is a view illustrating the foot operated I the hand operated master 7 master cylinder and cylinder cooperating therewith comprising longitudinal vertical sections through the two master cylinders and disclosing further details as to the master cylinders shown in Figure l;

Figure 3 is a longitudinal vertical section through a master cylinder illustrating another embodiment of the invention in which the entire compression of the liquid is effected in a single compression chamber;

Figure 4 is a view similar to Figure 3 showing the structure. of Figure 3 at the end of the stroke of the piston; and

Figure 5 is a fragmentary vertical section show- I details of the parts ing a portion of a master cylinder similar to a master cylinder of Figures 3 and 4 and illustrating a modification of certain which may be employed.

Before proceeding to a detailed description of practicing the invention I provide 'a*hydraulic system'for the automobile including any suitable piping leading to the wheel brakes. In addition to this, I provide foot-operated means for raising the pressure in the piping. I also provide handoperated means for raising the pressure developedin the piping. Referring more particularly to the parts and especially to'Figure 1, I represents the piping of a hydraulic system leading to the wheel brakes indicated at 2. In should be understood that it is merely a diagram and at the forward wheels the piplng would include the usual flexible connections to permit the wheels to be moved in steering.

be understood that in,

connection with this figure it vified with a supply port raise in pressure The piston of the In connection with the hydraulic system I include a pressure developing means which is preferably in the form of a master cylinder I15 which is mounted on the car frame 4 and arranged in such a way that it can be actuated by a foot pedal 5 one arm of which isconnected to the piston I18. This pressure developing device preferably includesthe cylinder. I15 connected to the cylinder I94 by means of the pipe line 294.-

boostercylinder I94 is operated by the second lever 25 which is preferably a hand lever mounted at convenient reach of a driver of the car. In the present instance as illustrated in Figure 1, this lever is located at the left side. However, it should be understood that in practice it may be located if desiredon the right side so as to be. operated by the right hand of the driver. The hand operated arm of this leveris relatively long. The outlet 206 from the upper side of the cylinder I94 is connected by the pipe 201 (see Figures land2) with the part of the piping system which that connects with the wheel brakes.

In the arrangement shown in Figures 3 and 4, I employ a single cylinder for developing a high pressure. The characteristic feature of this cylinder is that the advance of the plunger causes a considerable boost of pressure in the pressure chamber after which the further movement of the plunger greatly raises this pressure. At the same time the portion of the piston that causes the boosting effect is relieved of pressure so that in the latter part of the movement of the plunger, the plunger. is developing no unnecessary resistance.

In this embodiment of the invention, I also embody the reservoir in the cylinder casting, thereby producing a very compact structure.

Referring to Figure 3, I48 indicates a cylinder, the forward end of which is formed with a com pression cha ber I49 closed at its lever end with I50 through which is guided the reduced forward end I5I of a plunger I52. Back of the chamber I49 is provided a boosterchamber I53 in which moves a piston head I54 carried on leather I55. Areservoir chamber I56 is formed 'over the cylinder and, provided with a spring pressed relief valve I51 which opens upwardly to relieve pressure existing in the booster chamber I53. A spring I51a for valve I51 has sufiicient force so as to hold about fifteen pounds of pressure in the chamber I53, this being low enough to allow the brake return springs normally to hold the brakes in the released position. The valve chamber I58 under this relief valve is pro- I59 that passes through the wall of the cylinder just in advance of the cup leather I55. The inner end of the plunger I52 has a-bore I50with radial ports I6I that are supplied withliquid from the booster chamber I53 through a port I62 in the head I50.

is forced forwardly, pressure is developed in the booster chamber I53 which passes through,

the ports I82 and I6I into the compression chamber I49, the pressure in which is raised. This may be considerable due to the movement of the head I54. After the port I6I passes the .cup leather I63 closing the outer end of the chamber I49. liquid in the chamber I49 becomes trapped and the further rise in pressure is caused bythefurther advance of the reduced portion I5I of the plunger.

The wall of the chamber I53 is provided with a byp p IBM v gan in et at H near operation of the plunger I52 and provided with a cup When the plunger I52 The forward shaft I83 of the plunger I18 the head I50 and having an outlet at I65 near the position of rest of the piston head I54. In the the cylinder after the boosting effect has been attained in the chamber I49 by the advance of the head I54, the pressure in the forward end of the chamber I53 is relieved as soonas the head I54 passes the point I65. In other words, the latter part of the stroke of the piston head I54 is bypassed to relieve the pressure in front of it and permit all of the force of the operator of the brake to be applied thereafter to the piston I5I, to raise the pressure in the compression chamber I49.

The spring of the relief valve I51 will determine the maximum initial pressure that can exist in the chamber I53, by reason of the presence of the port I59.

The operating liquid in the chamber I53 and the connected pipe stem! is replenished on the return stroke of the plunger I5I by reason of the fact that liquid in the reservoir I55 can pass through the port I66 into the chamber I61 formed in the cylinder I48 back of the piston I54. Any operating liquid passing into the chamber I51, however, is prevented from leaking out at the back end of the plunger by reason of a cupleather I58 carried by the plunger.

In Figure 5 I illustrate another embodiment of my invention. I may provide a fixed head I69 with .a longitudinal duct I10 formed in the guide opening for the plunger III and a similar longitudinal duct I12 is provided in the end of the plunger I1I that projects into the compression chamber I13 beyond the guide head I69.

In the position of rest, that is to say, in the retracted position of the plunger I1I, these ports I10 and I12 register together at the point I14, but as soon as the slight advance of the plunger I1I has taken ,place, the communication between these ports is cut off. In other words, the port I10 does not pass all the way through the fixed head I59 and in the position of rest there is a slight overlap of these ports.

The plunger I1I is 215 carrying a cup leather 216 adapted to reciprocate in the cylinder 211. The cylinder 211 is formed with a portion 218 having a bore of relatively small diameter and a portion 219 having a bore of relatively large diameter. The piston head 215, together with the cup leather 216 makes a liquid tight fit in the bore 218, but in its forward position is spaced from the walls of the bore 219. As soon as the piston head 215 passes the junction between the two bores in its forward movement, liquid is allowed to by-pass around the piston head to the rear thereof whereupon the pressure exerted upon the fiuid in the system is the relatively high pressure developed by the plunger I1 I.

In Figure 2 I illustrated another embodiment of the booster cylinder in which I omit the bypass port I55.

Referring to'Figure 2, the cylinder I15 has a rear booster chamber I16 and a forward compression chamber I11. In the normal position of the plunger I18 the piston I19 for the booster chamber is located just to the rear of port I through the cylinder wall that leads under a relief valve I8I that opens into a reservoir I82.

through a fixed head I84 into the compression chamber I11, being provided with a cup leather packing ring I85 held against the fixed head by a coil spring I88. The shaft I83 of the plunger fits loosely in the head, as indicated at I81 and slides the end of the shaft I83 is formed with a central chamber I88 with ports I89 through its wall, which in the retracted position of the plunger permit the operating liquid to pass through from the chamber I16 into the chamber I11. In order to insure ample supply of liquid to the chamber I11, if desired, the fixed head may be provided with ports I98 that admit the liquid to the outer face of the cup leather I85. These features insure that the chamber I11 will always be maintained full of the operating liquid. With a cylinder having the features of construction illustrated in Figure 11, when the plunger I18 is advanced by applying the foot pedal, as soon as the cup leather I9I crosses the port I89 the pressure will rise in the chamber I16 and the fluid will flow through chamber I88 into the interior of the compres- The cup leather I85 will operate as a check valve to sustain any pressure developed in the compression chamber I11.

I Having exerted foot on the foot pedal, the operator of the brake can then permit a slight backward movement of the plunger I18. This will relieve the pressure in the chamber I16 but on account of the smaller diameter of the extension or shaft I83 of this plunger, will not substantially reduce the pressure 'in the chamber I11. In other words, this cylinder enables the operator to develop a considerable pressure in the pressure chamber I 11 through the assistance of the forward movement of the piston I19 of larger diameter, but by reason of the reduced pressure in the chamber I16 occasioned by a slight let-up of the pressure on the pedal, the high pressure being held by the foot, isexerted only on the area of the end of the shaft I83. For example almost infinitesimal-release of the foot pedal will on account of the incompressibility oi the liquid reduce the pressure in I16 to atmospheric pressure; while on account of the slight give of the brake lining. slight expansion of the conduits,.

and drum, the etc. substantially full pressure will be retained in I11. I

The operating liquid under pressure would pass out of the chamber I11 through an outlet I92 connected to a pressure chamber I93 by a pipe 294. This pressure chamber I93 is in the forward end of a cylinder I94 having a plunger I95 actuated by a hand lever, and the plunger I95 has a rear pistl chamber I91 of substantially the same diameter as the chamber I93. The reduced forward extension or shaft I98 of the plunger passes loosely through a fixed head I99 so that when the plunger I95 moves forward, liquid in it is forced through the annular clearance space 289 into the chamber I 93, which assists in raising the pressure in the chamber I93. It is to be understood in the normal operation of the brake the Y plunger I18 is first operated by the foot pedal so as to develop substantial brake applying pressure at the brakes and when that pressure has been developed the operator by a slight release of the pedal can hold the pressure applied by a small force due to the relatively small area of the piston I83. Thereafter operation of the hand lever operates the plunger I95 to develop much higher pressures, due to the fact that at such time the port in the extension I83 which the ports I89 and the a considerable efiort with the- I I96 working in a. rear casing having a connects the grooves I89 with the opening I88 has moved forward so'that it no longer is connected with the grooves I89 and instead is sealed by the. cup I85. Therefore the pressure developed by the plunger I95 and its pistons I 96 and I98 does not by-pass past the cup I85. The forward end of the chamber I91 is connected by a passage 28I to a closed reservoir 202. This reservoir would operate as an air trap to catch any air that might pass into the chamber I 91 on the back stroke of the plunger. Such air could, of course, pass the cup leather 203 which would operate as a check valve to prevent escape of the operating liquid past the head 196. If the level, indicated by the line 284 of the operating liquid, is maintained highup in the reservoir 202, it is evident that the plunger I 96 might assist considerably in developing the desired working pressure in the chamber I93.

However, in the operaticn of this cylinder it is impossible to build up a'pressure in the chamber 202 higher than the working pressure of the system because on the back stroke of the plunger I95. the pressure in the chamber I91 and in the reservoir 282 would be relieved through the clearance space at 290 into the chamber I93 and communicated back through the pipe indicated by the line I94 to the chamber I11, and thence relieved through the port I89 to the chamber I16, and

thence to the reservoir I82, through the relief valve I8I.

A cup leather 205, provided on the forward face of the fixed head I99, is held in place by a coil spring 285. The chamber I93 is provided with an outlet 286 that indicated by the line'291, ing devices at the wheels.

It is understood that the embodiment of the.

invention described herein is only one of the many embodiments this invention may take, and I do not wish to be limited invention, nor in the claims, to the particular embodiment set forth.

I claim:

1. In a master cylinder for hydraulic brakes, a casing having a compression chamber and a booster chamber having substantially the same diameter as said compression chamber with a head separating said chambers, a plunger having a head sliding in the booster chamber for developing pressure therein at the commencement of the forward stroke of the plunger andhaving a cylindrical extension passing through the firstnamed head into the compression chamber, means for opening communication through the cylindrical extension of the plunger between the booster chamber and the compression chamber when the plunger is in its retracted position. and means for by-passing the liquid from in front of the head of the plunger after the pressure in the compression chamber has be n boosted by the advance of the rear head of the plunger, said compression chamber having means for connecting the same to the brakes.

2. In a master cylinder for hydraulic brakes, a compression chamber and a booster chamber having substantially the same d ameter as said compression chamber with a head separating said chambers, a plunger having a head sliding in the booster chamber for developing pressure therein at the commencement of theforward stroke of the plunger and having a cylindrical extension passing through the firste named head into the compression chamber, means for opening communication through the cylindri is-connected by a pipe,

with the brake actuatin the practice of the -extension of reduced in the rear chamber and enables the 4- cal extension of the plunger between the booster chamber and the compression chamber when the plunger is in, its retracted position, means for bypassing the liquid from in front of the head of the plunger after the pressure in the compression chamber has been boosted by the advance of the head of the plunger, said compression chamber having means for connecting the same to the brakes, a reservoir having a port leading therefrom into the booster cylinder just in advance of the head of the plunger, and having a relief valve associated therewith for determining the initial operating pressure of the booster chamber'and the compression chamber.

3. In a hydraulic brake apparatus, the combination of a master cylinder having, a booster chamber and a compression chamber with a head separating the same and having a feed chamber to the rear of the booster chamber, a plunger with a cylindrical extension guided to slide through the said head, said plunger having a head separating the feed chamber from the booster chamber, a supply reservoir for' the operating liquid communicating with the feed chamber, said booster chamber having a port through the wall thereof just in advance of the head of the plunger when in its retracted position, with a'relief valve associated with the port for admitting liquid from the booster chamber into the reservoir, said cylindrical extension and said first-named head havin communicating ports for admitting liquid from the booster chamber into the compression chamber in the retracted position of the plunger, said compression chamber having means for connecting the same with the brakes. 4. A master cylinder for hydraulic brakes, having a forward compression chamber and a rear head separating the same, a plunger having an diameter sliding through the fixed head and having a piston head of larger diameter working in the rear chamber, check means associated with the fixed head permitting liquid under pressure to pass through into the forward compression chamber but checking return flow of the same, said forward chamber having an outlet leading to the brakes, said liquidfrom the rear chamber into the forward chamber and thereby raise the pressure in the forward chamber, said parts cooperating so that a slight rearward movement of the plunger after the pressure has developed, relieves the pressure pressure in the forward chamber to be sustained by exerting a reduced force on the plunger.

5. A master cylinder for hydraulic brakes, having a forward compression chamber and a rear compression chamber with a substantially fixed head separating the same, a plunger having an extension of reduced diameter sliding through the fixed head and having a piston head of larger diameter working in the rear chamber, check compression chamber with a substantially fixed plunger operating on the forward stroke to force means associated with the fixed head permitting liquid under pressure to pass through into the forward compression chamber but chec 'ng return flow of the same, said forward chamber having an outlet leading to the brakes, said plunger operating on' the forward stroke to force liquid from the rear chamber into the forward chamber and thereby raise the pressure in the forward chamber, said parts cooperating so that a slight rearward" movement of the plunger after the pressure has developed, relieves the pressure in the rear chamber and enables the pressure in the forward chamber to be sustained by exerting a reducedforce on the plunger, and means for establishing communication between the forward and rear chambers when the plunger is in its retracted position.

6. A master cylinder for hydraulic ing a forward compression chamber and a rear compression chamber with a substantially fixed head between the same, a plunger with a head sliding in the rear chamber and having a reduced extension passing through the fixed head into the forward compression .chamber, the rear end of the rear chamber beyond the plunger head being open to the atmosphere, said rear having a closed air-tight chamber communicating therewith and said fixed head having check liquid under pressure to pass from the rear chamber into the forward chamber when the plunger is moved forwardly to increase the pressure in the forward chamber.

'7. In a hydraulic brake apparatus, the combination of a master cylinder having a booster chamber and a compression chamber having substantially the same diameter as said booster chamber with a head separating the same and having a feed chamber to the rear of the booster chamber, a plunger with a cylindrical extension guided to'siide through the said head, said plunger having a head separating the feed chamber from the booster chamber, asupply reservoir for the operating liquid communicating with the feed chamber, said booster chamber having a port through the wall thereof just in advance of the head of the plunger when in its retracted position, with a relief valve associated with the port for admitting liquid from the booster chamber into the reservoir, said cylindrical extension and said firstname.d head having communicating ports for admitting liquid from the booster chamber into the compression chamber in the retracted position of the plunger, said compression chamber having means for connecting the same with the brakes, said booster chamber having a bypass port operating after the plunger head has liquid'around the same and relieve the pressure in front of the plunger head while the cylindrical extension of the plunger is developing the operating pressure in the compression chamber.

EUGENE G. CARROLL.

brakes havchamber CERTIFICATE OF CORRECTION. Patent No. 2,102,851 December 21, 1957.

" I Y I EUGENE G. CARROLL. V

It is hereby certified that error appears in the printed specification of the abovenumbered patent requiring correction as follows: Page =5, second column, line 62, claim 1, strike out the word "rear"; and that. the said I Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 15th day of Marchg A. D. 19 8.

Henry Van Arsda le, (Seal) Acting Commissioner of Patents. 

